1. Field of the Invention
The present invention relates to a semiconductor device, in particular, the present invention relates to an organic light emitting device (OLED) having a light emitting element formed on a substrate having an insulating surface. Further, the present invention relates to an organic light emitting module on which ICs and the like, including a controller, are mounted to an organic light emitting panel. Note that the terms organic light emitting panel and organic light emitting module both refer to light emitting devices in this specification. The present invention additionally relates to an apparatus for manufacturing the light emitting device.
In this specification, semiconductor devices correspond to general devices functioning by use of semiconductor characteristics. Therefore, a light emitting device, an electro-optical device, a semiconductor circuit and an electronic device are all included in the category of the semiconductor device.
2. Description of the Related Art
Techniques of forming TFTs (thin film transistors) on substrates have been progressing greatly in recent years, and developments in their application to active matrix display devices is advancing. In particular, TFTs that use polysilicon films have a higher electric field effect mobility (also referred to as mobility) than TFTs that use conventional amorphous silicon films, and therefore high speed operation is possible. Developments in performing control of pixels by forming driver circuits made from TFTs that use polysilicon films on a substrate on which the pixels are formed have therefore been flourishing. It has been expected that various advantages can be obtained by using active matrix display devices in which pixels and driver circuits are mounted on the same substrate, such as reductions in manufacturing cost, miniaturization of the display device, increases in yield, and increases in throughput.
Furthermore, research on active matrix light emitting devices using organic light emitting elements as self light emitting elements (hereinafter referred to simply as light emitting devices) has become more active. The light emitting devices are also referred to as organic EL displays (OELDs) and organic light emitting diodes (OLEDs).
TFT switching elements (hereinafter referred to as switching elements) are formed for each pixel in active matrix light emitting devices, and driver elements for performing electric current control using the switching TFTs (hereinafter referred to as electric current control TFTs) are operated, thus making EL layers (strictly speaking, light emitting layers) emit light. For example, a light emitting device disclosed in JP 10-189252 A is known.
Organic light emitting elements are self light emitting, and therefore have high visibility. Backlights, necessary for liquid crystal display devices (LCDs), are not required for organic light emitting elements, which are optimal for making display devices thinner and have no limitations in viewing angle. Light emitting devices using organic light emitting elements are consequently being focused upon as substitutes for CRTs and LCDs.
Note that EL elements have a layer containing an organic compound in which luminescence develops by the addition of an electric field (electroluminescence) (hereinafter referred to as EL layer, an anode, and a cathode. There is light emission when returning to a base state from a singlet excitation state (fluorescence), and light emission when returning to a base state from a triplet excitation state (phosphorescence) in the organic compound layer, and it is possible to apply both types of light emission to light emitting devices manufactured by the manufacturing apparatus and film formation method of the present invention.
EL elements have a structure in which an EL layer is sandwiched between a pair of electrodes, and the EL layer normally has a laminate structure. A xe2x80x9chole transporting layer/light emitting layer/electron transporting layerxe2x80x9d laminate structure proposed by Tang et al. of Eastman Kodak Co. can be given as a typical example. This structure has extremely high light emitting efficiency, and at present almost all light emitting devices undergoing research and development employ this structure.
Further, a structure in which: a hole injecting layer, a hole transporting layer, a light emitting layer, and an electron transporting layer are laminated in order on an anode; or a hole injecting layer, a hole transporting layer, a light emitting layer, an electron transporting layer, and an electron injecting layer are laminated in order on an anode may also be used. Fluorescent pigments and the like may also be doped into the light emitting layers. Further, all of the layers may be formed by using low molecular weight materials, and all of the layers may be formed by using high molecular weight materials. The layers may also include inorganic materials such as silicon.
Note that all layers formed between a cathode and an anode are referred to generically as EL layers in this specification. The aforementioned hole injecting layer, hole transporting layer, light emitting layer, electron transporting layer, and electron injecting layer are therefore all included in the category of EL layers.
Both low molecular weight organic compound materials and high molecular weight (polymer) organic compound materials are undergoing research as organic compound materials for EL layers (strictly speaking light emitting layers) which can be regarded as a main EL element.
Ink jet methods, evaporation, and spin coating are known as methods for forming films of these organic materials.
However, with these methods the film formation precision is not very high. Wide gaps are therefore designed between different pixels, and insulators referred to as banks are formed between pixels, when considering the manufacture of full color, flat panel displays using red, green, and blue colors of light emission.
Further, the demands for high definition, high aperture ratio, and high reliability are increased for full color flat panel displays using red, green, and blue color light emission. These demands become a big problem, however, in that the pitch between pixels becomes finer along with making the light emitting device higher in definition (increasing the number of pixels) and reducing the size of the light emitting device. Furthermore, the demands for increases in productivity and reductions in cost also increase.
An object of the present invention is therefore to achieve high definition, and a high aperture ratio, in a full color flat panel display using red, green, and blue color light emission, without depending on the organic compound layer film formation method or the film formation precision, by intentionally making a portion of different organic compound layers of adjacent light emitting elements overlap with each other.
Note that, although the luminance of light emission in the portions wherein parts of different organic compound layers overlap with each other falls to approximately 0.1% of its normal value, and the amount of electric current flowing there also drops to 0.1% of its normal value, it is possible to have light emission of an order capable of being sufficiently recognized, provided that a high voltage (equal to or greater than approximately 9 V) is applied.
According to a structure 1 of the present invention disclosed in this specification, there is provided a light emitting device comprising a plurality of light emitting elements, each having a cathode, an organic compound layer contacting the cathode, and an anode contacting the organic compound layer, in which one light emitting element has: a first light emitting region structured by the cathode, the organic compound layer contacting the cathode, and the anode contacting the organic compound layer; and a second light emitting region structured by the cathode, a laminate organic compound layer contacting the cathode, and the anode contacting the laminate organic compound layer.
In the above-mentioned structure 1, the laminate organic compound layer is a laminate layer of: the organic compound layer in the first light emitting region; and an organic compound layer of a light emitting element adjacent to the one light emitting element and having a different color light emission therefrom.
Further, three types of light emitting elements are suitably disposed for full color RGB, and according to a structure 2 of the present invention disclosed in this specification, there is provided a light emitting device comprising a plurality of light emitting elements, each having a cathode, an organic compound layer contacting the cathode, and an anode contacting the organic compound layer, in which a first light emitting element having a first organic compound layer, a second light emitting element having a second organic compound layer, and a third light emitting element having a third organic compound layer are arranged, and a portion of the first organic compound layer and a portion of the second organic compound layer overlap with each other in the first light emitting element.
Also, according to a structure 3 of the present invention disclosed in this specification, there is provided a light emitting device comprising a plurality of light emitting elements, each having a cathode, an organic compound layer contacting the cathode, and an anode contacting the organic compound layer, in which: a first light emitting element having a first light emitting layer, a second light emitting element having a second light emitting layer, and a third light emitting element having a third light emitting layer are arranged; a portion of the first organic compound layer and a portion of the second organic compound layer overlap with each other in the first light emitting element; and a portion of the second organic compound layer and a portion of the third organic compound layer overlap with each other in the second light emitting element.
Also, in the above-mentioned structure 2 or 3, the first light emitting element emits light of one color selected from the group consisting of red, green, and blue. Also, the first light emitting element, the second light emitting element, and the third light emitting element each emit light having a mutually different color.
Further, it is preferable to tightly seal the entire light emitting element using a sealing substrate, for example a glass substrate or a plastic substrate, during sealing in the structures 1, 2, and 3.
There is a problem with light emitting devices in that external light (light from outside of the light emitting device) made incident to pixels which are not emitting light is reflected by rear surfaces of the cathodes (surfaces contacting the light emitting layer), and the rear surfaces of the cathodes act as a mirror, reflecting external scenery in observation surfaces (surfaces toward an observer). Further, although circularly polarizing films are bonded to the observation surfaces of the light emitting device in order to avoid this problem, the circularly polarizing films have an extremely high cost, and this is a problem in that it invites an increase in manufacturing costs.
An object of the present invention is therefore to prevent turning the light emitting device into a mirrored surface without using a circularly polarizing film, and to provide a low cost light emitting device in which manufacturing costs for the light emitting device are thus lower. Low cost color filters are used by the present invention as a substitute for the circularly polarizing films. It is preferable to provide color filters in the light emitting device for each of the structures 1, 2, and 3 corresponding to each of the pixels in order to increase color purity. Furthermore, black color filter portions (black color organic resins) may also be formed overlapping the portions located between the light emitting regions. In addition, the black color filter portions may also overlap with the portions in which parts of different organic compound layers overlap with each other.
Note that the color filters are formed in the emission direction of the emitted light, that is between the light emitting elements and the observer. For example, color filters may be bonded to the sealing substrate for cases in which light does not pass through the substrate on which the light emitting elements are formed. Alternatively, color filters may be formed on the light emitting element substrate if light passes through the light emitting element substrate. Circularly polarizing films thus become unnecessary.
Further, the biggest problem in putting EL elements to practical use is that the element lifetime is insufficient. Element degradation also becomes a large problem as EL layer degradation occurs with the appearance of dark spots spreading along with long time light emission.
To solve this problem, the present invention employs a structure covered with a protective film made from a silicon nitride film or a silicon oxynitride film in which a silicon oxide film or a silicon oxynitride film is formed as a buffer layer in order to relieve stress in the protective film.
According to a structure 4 of the present invention, there is provided a light emitting device comprising a plurality of light emitting elements, each having a cathode, a an organic compound layer contacting the cathode, and an anode contacting the organic compound layer, in which: the anode is made from a transparent conductive film; and the anode is covered with a laminate of a buffer layer and a protective film.
In the above-mentioned structure 4, the buffer layer may be an insulating film having as its main constituent silicon oxide or silicon oxynitride formed by sputtering (RF sputtering or DC sputtering) or by a remote plasma method, and the protective film may be an insulating film having silicon nitride or silicon oxynitride as its main constituent formed by sputtering.
In addition, the aforementioned structure 4 is extremely useful for cases in which a transparent conductive film (typically ITO) is used as a cathode or an anode and a protective film is formed thereon. Note that, although there is a danger that impurities contained in the transparent conductive film (such as In, Sn, and Zn) will mix into a silicon nitride film contacting the transparent conductive film if the silicon nitride film is formed by sputtering, the impurities can be prevented from mixing into the silicon nitride film by forming the buffer layer of the present invention between the two films. The mixing in of impurities (such as In and Sn) form the transparent conductive film can be prevented by forming the buffer layer in accordance with the structure 4, and a superior protective film having no impurities can be formed.
Further, it is preferable to use different chambers for the buffer layer and the protective film in a method of manufacturing for achieving the structure 4. A structure relating to a method of manufacturing of the present invention is a method of manufacturing a light emitting device having a plurality of light emitting elements, each light emitting element having a cathode, an organic compound layer contacting the cathode, and an anode contacting the organic compound layer. After forming the anode from a transparent conductive film and the buffer layer covering the anode using the same chamber, the protective film is formed on the buffer layer using a different chamber.
Further, structures with two different light emission directions can be considered for an active matrix light emitting device. One is a structure in which light emitted from an EL element passes through an opposing substrate and out to enter the eye of an observer. The observer can recognize an image from the opposing substrate side in this case. The other structure is one in which light emitted form an EL element passes through an element substrate and out to enter the eye of an observer. In this case the observer can recognize an image from the element substrate side.
The present invention provides a manufacturing apparatus capable of making both of these structures.
A structure 5 of the present invention according to the present invention relates to a manufacturing apparatus including: a loading chamber; a first conveyor chamber coupled to the loading chamber; an organic compound layer film formation chamber coupled to the first conveyor chamber; a second conveyor chamber coupled to the first conveyor chamber; a metallic layer film formation chamber coupled to the second conveyor chamber; a transparent conductive film formation chamber; a protective film formation chamber; a third conveyor chamber coupled to the second conveyor chamber; a dispenser chamber coupled to the third conveyor chamber; a sealing substrate loading chamber; and a sealing chamber.
In the above-mentioned structure 5, the transparent conductive film formation chamber is provided with a plurality of targets including at least a target made from a transparent conductive material and a target made from silicon. Also, in the above-mentioned structure 5, the transparent conductive film formation chamber is provided with an apparatus for forming a film by a remote plasma method.
Further, a substrate on which a drying agent is bonded is placed in the sealing substrate loading chamber in the structure 5. In addition, there is a vacuum exhaust system in the sealing substrate loading chamber.
Further, there are also vacuum exhaust systems in the first conveyor chamber, the second conveyor chamber, the third conveyor chamber, and the sealing chamber.
Furthermore, the structure 4, in which the buffer layer and the protective film are formed, can be manufactured with good throughput by using the manufacturing apparatus shown in the structure 5.